The invention is directed to the dental area and relates to a container for preparing and/or dispensing dental compositions.
Such containers are used especially for producing dental preparations by mixing two or more reactive materials and for dispensing the finished preparation direct at the location to be treated, such as a cavity in a tooth.
U.S. Pat. No. 3,907,106 discloses a container for dispensing dental compositions, which comprises a container body forming a compartment, a piston axially movable in the body and defining a rear end of the compartment, and a dispensing nozzle disposed at a front end of the body. The container as supplied by the manufacturer to the user, for instance the dentist, is charged in such a way that one of the two components to be mixed with each other, which is a powder material, is contained in the mixing compartment and the other, liquid component is contained in a bag disposed beneath a clip which is arranged on the side of the mixing compartment.
In use, the clip is urged transversely of the longitudinal axis of the mixing compartment so that the bag is broken and discharges its content into the interior of the mixing compartment through an opening provided in the mixing compartment wall. Then the container is rapidly reciprocated by means of a shaker in order to react the two components with each other by mixing. Subsequently, the completely mixed dental preparation, which is now ready for use, is dispensed direct at the location to be treated through the nozzle which is integrally formed with the front end of the mixing compartment by pushing the piston in the longitudinal direction of the mixing compartment, after a pin which seals the container during transport, storage and mixing has previously been withdrawn from the front end of the nozzle.
In the known container the nozzle extends in the longitudinal direction of the mixing compartment. Since this position is hardly ever favourable to direct insertion in a dental cavity, it has been found that in practice the assistant will in any case bend the nozzle prior to use by the dentist even if this is not really necessary from the point of view of application. The material of the nozzle wall will thereby be considerably overstretched, which sometimes even results in breakage.
Bending causes a cross-sectional constriction of the nozzle, which in turn leads to segregation of the materials; this is due to the fact that larger material particles pile up in front of the constriction, so that less viscous ingredients are urged through first. Such mixtures which do not have the proper mixing ratio may be useless and may endanger the success of the dental treatment. Sometimes the dam-up is excessive so that the container becomes completely blocked.
In accordance with the German Laid-Open Application No. 2,741,184 it has been attempted to overcome the already recognized above-mentioned difficulty by making at least the dispensing nozzle, which is integrally formed with the mixing compartment, flexible and surrounding it by a rigid two-part protective cover. Apart from the fact that such a protective cover represents an undesirable increase in the number of parts which must be manufactured and have to be manipulated during application, its provision is impossible with some types of shakers due to the design of the mixing fork thereof. Furthermore, it is difficult with the known container to provide the mixing compartment itself with sufficient rigidity so that it will withstand the pressure applied on dispensing of the finished material by means of the piston, and at the same time to provide the dispensing nozzle integrally formed on the mixing compartment with sufficient flexibility so that the cross-sectional constriction upon bending may be prevented.
From the European Patent Application, Publication No. 63,891, there has been known a mixing and dispensing container for dental preparations, in which the dispensing nozzle is integrally formed with the mixing compartment at an angle to the longitudinal axis of said compartment. Although for a number of applications this position of the nozzle may well be more favourable than the nozzle which conventionally extends in the longitudinal direction of the mixing compartment, there is still the risk that the nozzle will be bent to move it to the respective most suitable position. Besides, this container also cannot be placed in a number of conventional shakers because of the obliquely extending rigid nozzle.
The same problem exists with the container of U.S. Pat. No. 3,907,106 referred to above, in which the nozzle extends axially from the compartment, unless the supporting fork of the shaker is provided with a hole. Apart from this, however, any straight forwardly or obliquely projecting nozzle is disadvantageous, because it substantially increases the overall length of the container and therefore cannot be used with shaking mechanisms protected by a hood which surrounds the supporting fork in relatively close relationship.
With containers of the type described above, in which the nozzle is sealed by a pin until the time of dispensing, there is the additional problem that while the nozzle should be slightly conical throughout its length and funnel-shaped in the entry region for reliable and convenient dispensing, dead spaces will result between the cylindrical pin and the nozzle wall in which the powder component settles during storage and subsequently does not participate in the mixing process. It has been observed that upon dispensing this unmixed material will sit on the strand, so that, unless it is removed, it is inserted first into the dental cavity and cannot properly be cured therein.
It is a general object of the present invention to eliminate at least some of the drawbacks existing with the prior art. As a more specific object, a container suitable for dispensing dental compositions is to be provided which, while consisting of a small number of single parts, allows a variation of the position of the dispensing nozzle without the risk of cross-sectional constrictions.